Turbofan engine performance recovery system and method

ABSTRACT

Methods and apparatus are provided for improving engine performance in a turbofan gas turbine engine following foreign object ingestion in turbofan gas turbine engines that include an intake fan that includes a plurality of fan blades, and that is disposed within and surrounded by a fan case. The occurrence of a foreign object ingestion by the turbofan gas turbine engine is detected and, upon detecting that a foreign object has been ingested, air is bled from a region proximate the blades of the intake fan through a slot in the fan case.

TECHNICAL FIELD

The present invention generally relates to turbofan jet engines, and more particularly relates to performance recovery systems and methods for turbofan jet engines.

BACKGROUND

Aircraft propulsion engines can be susceptible to foreign object ingestion events. Such events include, for example, ingestion of one or more birds by the engine intake section. The intake section includes an intake fan having a plurality of blades. Following an ingestion event, the fan blades have the potential to be deformed or damaged. Deformed or damaged fan blades may result in relatively large flow separation on the fan case. This can cause flow blockage and reduced engine performance, including undesirable engine thrust reduction.

To mitigate the likelihood of post-ingestion thrust reductions in aircraft propulsion engines, some government regulatory agencies mandate that certain aircraft propulsion engines be able to produce a minimum level of thrust after certain foreign object ingestion events, such as ingesting multiple birds. This mandated robustness is currently achieved passively by making certain fan components relatively stiffer than what may be necessary, thereby undesirably increasing engine weight, and thus overall operating costs.

Hence, there is a need for a system and method that mitigates the potential deleterious effects of a foreign object ingestion event. The present invention addresses at least this need.

BRIEF SUMMARY

In one embodiment, a turbofan engine intake assembly includes a fan case, an intake fan, a slot, and an annulus. The fan case is adapted to be mounted in an engine nacelle assembly, and includes an inner surface and an outer surface. The intake fan is mounted within the fan case and includes a plurality of radially extending fan blades. The slot extends through the fan case between the inner and outer surfaces, and at least partially extends around the fan case proximate the fan blades. The annulus is coupled to the outer surface and includes an inner surface that defines an annular plenum that is in fluid communication with the slot and atmosphere outside the fan case.

In another embodiment, a turbofan engine system includes a nacelle assembly, an intake section, a compressor section, a combustion section, and a gas turbine section mounted in the nacelle assembly. The intake section includes a fan case, an intake fan, a slot, and an annulus. The fan case is mounted in the engine nacelle, and includes an inner surface and an outer surface. The intake fan is mounted within the fan case and includes a plurality of radially extending fan blades. The slot extends through the fan case between the inner and outer surfaces, and at least partially extends around the fan case proximate the fan blades. The annulus is coupled to the outer surface and includes an inner surface that defines an annular plenum that is in fluid communication with the slot and atmosphere outside the fan case.

In yet another embodiment, a method of recovering engine performance in a turbofan gas turbine engine following foreign object ingestion is provided. The turbofan gas turbine engine includes an intake fan and a fan case. The intake fan is disposed within and is surrounded by the fan case and includes a plurality of fan blades. The method includes detecting when a foreign object has been ingested by the turbofan gas turbine engine. Upon detecting that a foreign object has been ingested, air is bled from a region proximate the blades of the intake fan through a slot in the fan case.

Furthermore, other desirable features and characteristics of the turbofan engine system performance recovery system and method will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

FIG. 1 depicts a functional block diagram of an embodiment of a turbofan gas turbine engine; and

FIG. 2 is a close-up view of a portion of the turbofan gas turbine engine of FIG. 1, depicting an embodiment of a portion of the engine intake section in more detail.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

Turning now to FIG. 1, a functional block diagram of an exemplary turbofan gas turbine engine is depicted. The depicted engine 100 is a multi-spool turbofan gas turbine propulsion engine, and includes an intake section 102, a compressor section 104, a combustion section 106, a turbine section 108, and an exhaust section 112. The intake section 102 includes an intake fan 114, which is mounted in a nacelle assembly 116. The intake fan 114 draws air into the intake section 102 and accelerates it. A fraction of the accelerated air exhausted from the intake fan 114 is directed through a bypass flow passage 118 defined between the nacelle assembly 116 and an engine cowl 122. This fraction of air flow is referred to herein as bypass air flow. The remaining fraction of air exhausted from the intake fan 114 is directed into the compressor section 104.

The compressor section 104 may include one or more compressors 124, which raise the pressure of the air directed into it from the intake fan 114, and direct the compressed air into the combustion section 106. In the depicted embodiment, only a single compressor 124 is shown, though it will be appreciated that one or more additional compressors could be used. In the combustion section 106, which includes a combustor assembly 126, the compressed air is mixed with fuel supplied from a non-illustrated fuel source. The fuel and air mixture is combusted, and the high energy combusted fuel/air mixture is then directed into the turbine section 108.

The turbine section 108 includes one or more turbines. In the depicted embodiment, the turbine section 108 includes two turbines, a high pressure turbine 128, and a low pressure turbine 132. However, it will be appreciated that the engine 100 could be configured with more or less than this number of turbines. No matter the particular number, the combusted fuel/air mixture from the combustion section 106 expands through each turbine 128, 132, causing it to rotate. As the turbines 128 and 132 rotate, each drives equipment in the engine 100 via concentrically disposed shafts or spools. Specifically, the high pressure turbine 128 drives the compressor 124 via a high pressure spool 134, and the low pressure turbine 132 drives the intake fan 114 via a low pressure spool 136. The gas exhausted from the turbine section 108 is then directed into the exhaust section 112.

The exhaust section 112 includes a mixer 138 and an exhaust nozzle 142. The mixer 138 includes a centerbody 144 and a mixer nozzle 146, and is configured to mix the bypass air flow with the exhaust gas from the turbine section 108. The bypass air/exhaust gas mixture is then expanded through the propulsion nozzle 142, providing forward thrust.

Though not visible in FIG. 1, the intake fan 114 is disposed within and surrounded by a fan case that is coupled to nacelle assembly 116. A close-up view of a portion of the intake section 102 in more detail is depicted in FIG. 2, and with reference thereto will now be described.

In addition to the intake fan 114, the depicted intake section 102 includes a fan case 202, a slot 204, and an annulus 206. The fan case 202, at least in the depicted embodiment, is mounted in the nacelle assembly 116 (not illustrated in FIG. 2), and includes an inner surface 208 and an outer surface 212. The depicted embodiment additionally includes a containment casing 214 and abradable lining 216, both of which are coupled to the fan case outer surface 212. It will be appreciated that the intake section could be implemented without one or both of the containment casing 214 and abradable lining 216, and that the depicted configuration of these elements, when included, is merely exemplary of one particular embodiment.

The intake fan 114 is mounted within the fan case 202 and includes a plurality of radially extending fan blades 218. It will be appreciated, however, that for clarity only a single fan blade 218 is depicted in FIG. 2. As is generally known, each fan blade 218 has a leading edge 222 and a trailing edge 224. The fan blades 218 are contoured between the leading edges 222 and trailing edges 224 to facilitate the above-described functionality of the intake fan 114; namely, to draw air into the intake section 102 and accelerate the air for subsequent use downstream.

The slot 204 is formed in, and extends through, the fan case 202 between the inner and outer surfaces 208 and 212. The slot 204 preferably extends circumferentially around the fan case 202 and thus circumferentially surrounds the fan blades 218. It will be appreciated, however, that the slot 204 could extend only partially around the fan case 202. Moreover, the slot 204 need not extend continuously around the fan case 202, but may be interrupted by various support structure, such as, for example, struts. The slot 204 is preferably disposed at least proximate the fan blades 218. In a particular preferred embodiment, the slot 204 is disposed between the leading edge 222 and trailing edge 224 of each fan blade 218. The specific location between the leading edges 222 and trailing edges 224 may vary depending, for example, on engine type. For example, in some embodiments the slot 204 may be located midway between the leading edges 222 and trailing edges 224, whereas in other embodiments the slot 204 may be disposed closer to either the leading edges 222 or trailing edges 224. It will be appreciated that the slot 204 may also be disposed slight upstream of the leading edges 224 or slight downstream of the trailing edges. The width of the slot 204 may also vary to meet desired performance.

No matter the specific location and width of the slot 204, the annulus 206 is coupled to the outer surface 212 of the fan case 202 at the location of the slot 204. The annulus 206 may be variously shaped and configured, but includes at least an inner surface 226 that defines an annular plenum 228. The annulus 206 is also configured such that the annular plenum 228 is in fluid communication with the slot 204, and at least selectively in fluid communication with the atmosphere 232 outside of the fan case 202. It will be appreciated that the annular plenum 228 may be selectively placed in fluid communication with the atmosphere 232 using any one of numerous techniques. In the depicted embodiment, however, a conduit 234 and a valve 236 are used.

The conduit 234 includes an inlet port 238 and an outlet port 242. The inlet port 238 is in fluid communication with the annular plenum 228, and the outlet port 242 in fluid communication with the atmosphere 232. The valve 236 is mounted on the conduit 234 between the inlet port 238 and the outlet port 242, and is movable to a plurality of valve positions. The valve positions include a closed position and a plurality of open positions. In the closed position the valve 236 fluidly isolates the conduit inlet port 238 and outlet port 242, and thereby prevents (or at least substantially prevents) air from flowing through the slot 204, into the annular plenum 228, and out the conduit 234 to the atmosphere 228. In any one of the open positions the conduit inlet port 238 and outlet port 242 are in fluid communication, which allows air to flow through the slot 204, into the annular plenum 228, and out the conduit 234 to the atmosphere 228.

The valve 236 is preferably moved to a valve position via a valve actuator 244, which is coupled to the valve 236 and which may be implemented using any one of numerous types of pneumatic, hydraulic, or electric type of actuators. No matter how it is specifically implemented, the valve actuator 244 is coupled to receive valve actuator commands and is configured, upon receipt of the valve actuator commands, to selectively move the valve 236 to one of the plurality of valve positions. The valve actuator commands that are supplied to the valve actuator 244 may originate from a manually actuated switch or knob 246, such as the one depicted in phantom in FIG. 2. Alternatively, in a preferred embodiment, the valve actuator commands originate from an engine control 248.

Before proceeding further, it is noted that a plurality of conduits 234 could extend between the annular plenum 228 and atmosphere 232, each having an associated valve 236. In FIG. 2, a second conduit 234 and second valve 236 are depicted in phantom; however, more than two conduits 234 and valves 236 could be included, if needed or desired. As FIG. 2 also depicts in phantom, one or more pumps 237 (only one depicted) could be included to help discharge air from the annular plenum 228. It will be appreciated that a pump 237 could be associated with each conduit 234, a pump 237 could be associated with a plurality of conduits 234, and that some conduits 234 could have an associated pump 237 while others do not.

The engine control 248, which may be implemented as a full-authority digital engine control (FADEC), an electronic engine control (EEC), or any one of numerous other engine control configurations, receives data from various sensors 252. The sensors 252 sense various parameters such as, for example, engine throttle position, fuel flow, and various parameters within with the turbofan gas turbine engine 100. The engine control 248, based at least in part on these parameters, controls the operation of the turbofan gas turbine engine 100.

In addition to the above, the depicted engine control 248 is configured to detect a foreign object ingestion event, such as a bird ingestion event. The engine control 248 is further configured, upon detecting a foreign object ingestion event, to supply valve actuator commands to the valve actuator 244 that will cause the valve 236 to move from the closed position to an open position. The manner in which the engine control 248 detects a foreign object ingestion event may vary. For example, in some embodiments the engine control 248, based on data from at least selected ones of the sensors 252, detects a performance degradation of the turbofan gas turbine engine 100. In other embodiments the engine control 248, based on data from at least selected ones of the sensors 252, detects a change in the air pressure around the intake fan 114. No matter the specific foreign object ingestion event detection scheme that is used, when the valve 236 is subsequently moved to an open position, air flows through the slot 204, into the annular plenum 228, and out the conduit 234 to the atmosphere 228.

It has been found that bleeding air through the slot 204, into the annular plenum 228, and out the conduit 234 to the atmosphere 228 following a foreign object ingestion event reduces the size of flow separations that may be induced by the potential damage the ingested object may have caused. As a result, engine performance is improved relative to conventional turbofan gas turbine engines, which do not include provisions for this flow path. Indeed, models of pre-ingestion event and post-ingestion event operations in a conventional turbofan gas turbine engine and in a turbofan gas turbine engine that embodies the instant invention show that post-ingestion event total pressure ratio and total temperature ratio in an inventive turbofan gas turbine engine are higher than those of conventional engine.

The system and method described herein mitigate the potential deleterious effects of a foreign object ingestion event. As a result, lighter intake fan components may be used to construct aircraft propulsion engines and/or additional margin may be provided for certain foreign object ingestion events, such as multiple bird ingestion events.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims. 

1. A turbofan engine intake assembly, comprising: a fan case adapted to be mounted in an engine nacelle assembly, the fan case including an inner surface and an outer surface; an intake fan mounted within the fan case and including a plurality of radially extending fan blades; a slot extending through the fan case between the inner and outer surfaces, the slot at least partially extending around the fan case proximate the fan blades; and an annulus coupled to the outer surface and including an inner surface that defines an annular plenum, the annular plenum in fluid communication with the slot and atmosphere outside the fan case.
 2. The turbofan engine intake assembly of claim 1, further comprising: a discharge conduit coupled to the annulus and including an inlet port and an outlet port, the inlet port in fluid communication with the annular plenum, the outlet port in fluid communication with the atmosphere outside the fan case.
 3. The turbofan engine intake assembly of claim 2, further comprising: a valve mounted on the discharge conduit and movable to a plurality of valve positions.
 4. The turbofan engine intake assembly of claim 3, further comprising: a valve actuator coupled to the valve, the valve actuator adapted to receive valve actuator commands and configured, upon receipt of the valve actuator commands, to selectively move the valve to one of the plurality of valve positions.
 5. The turbofan engine intake assembly of claim 1, wherein: each fan blade includes a leading edge and a trailing edge; and the slot is disposed between the leading edge and trailing edge of each fan blade.
 6. A turbofan engine system, comprising: a nacelle assembly; an intake section, a compressor section, a combustion section, and a gas turbine section mounted in the nacelle assembly, the intake section comprising: a fan case mounted in the nacelle assembly, the fan case including an inner surface and an outer surface; an intake fan mounted within the fan case and including a plurality of radially extending fan blades; a slot extending through the fan case between the inner and outer surfaces, the slot at least partially extending around the fan case proximate the fan blades; and an annulus coupled to the outer surface and including an inner surface that defines an annular plenum, the annular plenum in fluid communication with the slot and atmosphere outside the fan case.
 7. The turbofan engine intake assembly of claim 6, further comprising: a discharge conduit coupled to the annulus and including an inlet port and an outlet port, the inlet port in fluid communication with the annular plenum, the outlet port in fluid communication with the atmosphere outside the fan case.
 8. The turbofan engine system of claim 7, further comprising: a valve mounted on the discharge conduit and movable to a plurality of valve positions.
 9. The turbofan engine system of claim 8, further comprising: a valve actuator coupled to the valve, the valve actuator further coupled to receive valve actuator commands and configured, upon receipt of the valve actuator commands, to selectively move the valve to one of the plurality of valve positions.
 10. The turbofan engine system of claim 8, further comprising: a pump mounted on the conduit and configured to selectively pump air from the annulus.
 11. The turbofan engine system of claim 6, further comprising: an engine control coupled to, and configured to selectively supply the valve actuator commands to, the valve actuator.
 12. The turbofan engine system of claim 11, wherein the engine control is further configured to detect a foreign object ingestion event.
 13. The turbofan engine system of claim 12, wherein the engine control is further configured to supply the valve actuator commands upon detecting the foreign object ingestion event.
 14. The turbofan engine system of claim 6, wherein: each fan blade includes a leading edge and a trailing edge; and the slot is disposed between the leading edge and trailing edge of each fan blade.
 15. A method of improving engine performance in a turbofan gas turbine engine following foreign object ingestion, the turbofan gas turbine engine comprising an intake fan and a fan case, the intake fan disposed within and surrounded by the fan case and including a plurality of fan blades, the method comprising the steps of: detecting when a foreign object has been ingested by the turbofan gas turbine engine; and upon detecting that a foreign object has been ingested, bleeding air from a region proximate the blades of the intake fan through a slot in the fan case.
 16. The method of claim 15, wherein the step of detecting comprises detecting performance degradation of the turbofan gas turbine engine.
 17. The method of claim 15, wherein the step of detecting comprises detecting a change in air pressure around the intake fan.
 18. The method of claim 15, wherein the step of bleeding air comprises opening a valve that allows air from the region to flow to atmosphere.
 19. The method of claim 18, wherein the valve is opened automatically upon detecting that a foreign object has been ingested.
 20. The method of claim 15, wherein the step of bleeding air comprises pumping air from the region. 